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Why Do Enolate Anions Favor O-Alkylation over C-Alkylation in the Gas Phase? The Roles of Resonance and Inductive Effects in the Gas-Phase SN2 Reaction between the Acetaldehyde Enolate Anion and Methyl Fluoride
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2016-04-12 00:00:00 , DOI: 10.1021/acs.joc.6b00351 Christian G. Seitz 1 , Huaiyu Zhang 2 , Yirong Mo 2 , Joel M. Karty 1
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2016-04-12 00:00:00 , DOI: 10.1021/acs.joc.6b00351 Christian G. Seitz 1 , Huaiyu Zhang 2 , Yirong Mo 2 , Joel M. Karty 1
Affiliation
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Contributions by resonance and inductive effects toward the net activation barrier were determined computationally for the gas-phase SN2 reaction between the acetaldehyde enolate anion and methyl fluoride, for both O-methylation and C-methylation, in order to understand why this reaction favors O-methylation. With the use of the vinylogue extrapolation methodology, resonance effects were determined to contribute toward increasing the size of the barrier by about 9.5 kcal/mol for O-methylation and by about 21.2 kcal/mol for C-methylation. Inductive effects were determined to contribute toward increasing the size of the barrier by about 1.7 kcal/mol for O-methylation and 4.2 kcal/mol for C-methylation. Employing our block-localized wave function methodology, we determined the contributions by resonance to be 12.8 kcal/mol for O-methylation and 22.3 kcal/mol for C-methylation. Thus, whereas inductive effects have significant contributions, resonance is the dominant factor that leads to O-methylation being favored. More specifically, resonance serves to increase the size the barrier for C-methylation significantly more than it does for O-methylation.
中文翻译：
为什么在气相中，甲酸酯阴离子比O-烷基更倾向于O-烷基化？乙醛酸根阴离子和甲基氟在气相S N 2反应中的共振和感应作用
通过共振并朝向净活化屏障电感效应捐款计算确定用于气体-阶段S Ñ为了理解为什么该反应有利于O-甲基化，乙醛烯醇酸根阴离子和甲基氟之间的反应对于O-甲基化和C-甲基化都是如此。通过使用乙烯基外推法，确定了共振效应，以使阻挡层的尺寸增加，O-甲基化约为9.5 kcal / mol，C-甲基化约为21.2 kcal / mol。确定了感应效应，有助于增加势垒的尺寸，O-甲基化约为1.7 kcal / mol，C-甲基化约为4.2 kcal / mol。使用我们的块局部波动函数方法，我们确定共振的贡献对于O-甲基化为12.8 kcal / mol，对于C-甲基化为22.3 kcal / mol。因此，尽管归纳效应具有重大贡献，共振是导致O-甲基化的主要因素。更具体地，共振比C-甲基化显着更多地增加了C-甲基化的势垒的尺寸。
更新日期：2016-04-12
中文翻译：
为什么在气相中，甲酸酯阴离子比O-烷基更倾向于O-烷基化？乙醛酸根阴离子和甲基氟在气相S N 2反应中的共振和感应作用
通过共振并朝向净活化屏障电感效应捐款计算确定用于气体-阶段S Ñ为了理解为什么该反应有利于O-甲基化，乙醛烯醇酸根阴离子和甲基氟之间的反应对于O-甲基化和C-甲基化都是如此。通过使用乙烯基外推法，确定了共振效应，以使阻挡层的尺寸增加，O-甲基化约为9.5 kcal / mol，C-甲基化约为21.2 kcal / mol。确定了感应效应，有助于增加势垒的尺寸，O-甲基化约为1.7 kcal / mol，C-甲基化约为4.2 kcal / mol。使用我们的块局部波动函数方法，我们确定共振的贡献对于O-甲基化为12.8 kcal / mol，对于C-甲基化为22.3 kcal / mol。因此，尽管归纳效应具有重大贡献，共振是导致O-甲基化的主要因素。更具体地，共振比C-甲基化显着更多地增加了C-甲基化的势垒的尺寸。
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